1. Field of the Invention
The present invention relates to a coordinate input device for inputting two-dimensional coordinates, and more particularly to a coordinate input device preferably employed as a stick type pointing device for controlling a position of a cursor on a display of a computer.
2. Description of the Related Art
In general, a coordinate input device of this type has hitherto had a structure, as shown in FIGS. 6 and 7, in which four or two distortion gauges 3 composing a detection sensor are bonded to the four or two surfaces of a prismatic operating part 2 provided at the central part of a base 1, an annular connecting part 5a at the end of a cable 5 in which a plurality of leads 4 are arranged is fixed to the upper surface of the base 1 by being passed through the operating part 2, and the distortion gauges 3 are respectively connected to the leads 4 of the cable 5 by soldering. In the coordinate input device, the operating part 2 is formed with a hollow structure and serves as a distortion generating part. When force is exerted on the operating part 2 from the forward and backward directions and the right and left directions, the operating part 2 is distorted so that electric resistance value of each distortion gauge 3 changes. The signal of the electric resistance value is transmitted to a detection circuit (not shown) through the cable 5 to detect the direction and intensity of the force applied to the operating part 2, as disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 7-244559. The connection parts of the distortion gauges 3 and the cable 5 are protected by a protective layer 6 such as rubber.
When the above-described coordinate input device is employed as a stick type pointing device, the coordinate input device is mounted on the substrate of a keyboard input device by using leg parts 7 protruding onto the back surface of the base 1. Then, the operating part 2 is projected between the key caps of groups of key switches and covered with a cap 8 so as to enable to be operated by fingers of a user. Further, the other end of the cable 5 is connected to the control part of the computer. In such a stick type pointing device, operation of the operating part 2 by the fingers of a user through the cap 8 makes the signal of each of the distortion gauges 3 inputted to the control part. The control part calculates the direction of movement, the amount of movement, the moving speed, or the like of a cursor on a display on the basis of the signal from the distortion gauge 3 to control the position of the cursor.
However, upon assembling, according to the above-mentioned conventional coordinate input device, since a plurality of distortion gauges 3 are individually bonded to the operating part 2 of the base 1, and then, the respective distortion gauges 3 need to be soldered to the cable 5, a workability in assembling these members is extremely deteriorated. Besides, since the unevenness of positions where the respective distortion gauges 3 are bonded cannot be avoided, it has been undesirably difficult to ensure high accuracy.
Further, in recent years, a demand for the decrease in thickness of a portable personal computer such as a notebook personal computer, a mobile computer has been more and more increased. However, according to the structure of the conventional coordinate input device in which the distortion gauges 3 are stuck to the pole shaped operating part 2 as described above, the size of the distortion gauge 3 cannot be reduced to a dimension smaller than a prescribed dimension in view of its accuracy and there exists a limitation in reducing the height of the operating part 2. Therefore, it has been inconveniently impossible to meet the above-mentioned demand for the decrease in the thickness of the portable personal computer.
Furthermore, for example, Japanese Patent Application Laid-Open No. Hei 7-174646 discloses a pointing device of a type that an elastic plate is attached to a mount base supported at three points or four points, a pole shaped operating part is connected to the central part of the elastic plate, the elastic plate is used as a distortion generating body, and a plurality of distortion detecting resistance elements, that is to say, distortion gauges are disposed on the elastic plate. According to this pointing device, since the distortion gauges do not need to be stuck to the operating part, the height of the operating part can be reduced, which can contribute to the decrease in thickness of the portable personal computer. However, even this structure is no different from the conventional device in that, since a plurality of distortion gauges must be individually bonded to the device, the deterioration of accuracy due to the deterioration of workability in assembling the components or the unevenness in fixed positions of the distortion gauges cannot be avoided. Therefore, this structure does not provide a primary countermeasure. In addition, since not only the mount base needs to be specially prepared, but also a troublesome assembling work for attaching the elastic plate onto the mount base is required to increase the burden of cost. Furthermore, since the distortion gauges are arranged so as to be distributed in a wide range on the elastic plate, it is disadvantageously complicated and troublesome to handle or treat a cable connected to the distortion gauges. Thus, this brings about a new problem in that the installation workability in mounting the pointing device on a substrate of the keyboard input device is deteriorated.
The present invention has been made in view of the above problems of the conventional device and an object of the present invention is therefore to provide a coordinate input device in which a workability in assembling parts and accuracy can be improved and an operating part can be made compact without increasing the burden of cost or deteriorating an installation workability so as to remarkably contribute to the decrease in the thickness of a portable personal computer.
In order to achieve the above-described object, according to the present invention, a coordinate input device comprises a base having an plate shaped distortion generating part below a pole shaped operating part which are integrally formed; and a detection sensor having a plurality of distortion gauges and a plurality of leads connected to the distortion gauges which are integrally arranged on one plastic sheet, and is characterized in that the detection sensor has a structure in which the plurality of distortion gauges are put together so that the distortion gauges are bonded to the back surface of the distortion generating part of the base, and the plurality of leads are arranged in parallel and extended in one direction from the base.
In the coordinate input device thus constructed, only the detection sensor is bonded to the back surface of the distortion generating part of the base formed integrally therewith so that a plurality of distortion gauges and leads can be simultaneously attached thereto with high efficiency and high accuracy. Further, since it is not necessary to stick the distortion gauges to the operating part, the height of the operating part can be reduced as much as possible.
Further, according to the coordinate input device of the present invention, the number of the distortion gauges provided in the detection sensor may be two or four. When the four distortion gauges are provided on the detection sensor, they may be desirably put together in a cross shaped arrangement.
In this case, a cross index for indicating the central position of the four distortion gauges and the arrangement directions thereof is provided on the sheet of the detection sensor and a through hole of a square shape in section which passes through the distortion generating part from the upper end of the operating part is formed in the operating part of the base. Thus, the cross index is aligned with the through hole so that the detection sensor can be simply and accurately positioned.